The present invention relates to a technology for producing an image at a high speed by heat-developing a photothermographic material. The present invention is in particular beneficial in image production on a photothermographic material using a scanner or image setter suitable for photoengraving.
There are a variety of known photosensitive materials having on a support a photosensitive layer and capable of producing an image by image-wise light exposure. Among these, a material for producing an image by heat development can compose a system responsible for achieving environmental preservation and simplifying an image producing means.
A strong need for reducing the volume of the waste of processing solution has arisen in recent years in the field of photoengraving from viewpoints of environmental preservation and space saving. Thus a technology related to a photothermographic material for photoengraving has been desired, in which the material being such that allowing efficient light exposure with a laser image setter or laser imager, and providing a black image with a high resolution and sharpness. Such photothermographic material can provide the user with a more simple and environment-conscious image producing system using no solution-base process chemicals.
Exemplary methods for producing an image by heat development are, for example, found in U.S. Pat. Nos. 3,152,904 and 3,457,075 and xe2x80x9cThermally Processed Silver Systemsxe2x80x9d by D. Klosteraboer, Imaging Processes and Materials, Neblette""s 8th ed., edited by Sturge, V. Walworth and A. Shepp, Chapter 9, p.279, (1989). Such photothermographic material contains a reducible non-photosensitive silver source (e.g., organic acid silver salt), a catalytic amount of a photocatalyst (eg., silver halide) and a reducing agent for reducing silver, all of which being generally dispersed in an organic binder matrix. While the photothermographic material is stable at the normal temperature, it can produce a black silver image when heated, after light exposure, to a high temperature (e.g., 80. C. or above) through redox reaction of the reducible silver source (acts as an oxidant) with the reducing agent. The redox reaction is promoted by a catalytic action of a latent image produced by the light exposure. Silver produced from the reducible silver source within the exposed area is blackened, which creates a contrast to a non-exposed area to thereby produce an image.
Many of the conventional photothermographic material have an image producing layer formed by coating a coating liquid which contains as a solution medium an organic solvent such as toluene, methyl ethyl ketone (MEK) or methanol. Using an organic solvent as a solution medium, however, is not only hazardous to human body, but is also disadvantageous in terms of the production cost since it calls for additional process steps such as for recovering the solvent.
Thus a method for forming, using a water-base coating liquid, the image producing layer is proposed. For example, JP-A-49-52626 (the code xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-53-116144 disclose an image producing layer containing gelatin as a binder. In JP-A-50-151138, an image producing layer using polyvinyl alcohol as a binder is described. An image producing layer based. on a combined use of gelatin and polyvinyl alcohol is found in JP-A-60-61747. Still another example of an image producing layer relates to that using a water-soluble polyvinyl acetal as a binder described in JP-A-58-28737. Using such water-soluble binders allows the image producing layer to be formed with a water-base coating liquid and is beneficial from environmental and economic viewpoints.
For the purpose of obtaining a high-contrast photographic property, European Laid-Open Patent Publication No. 762,196 and JP-A-9-90550 disclose a photothermographic material containing, in addition to a photosensitive silver halide grain, a metal ion of Group VII or VIII, a complex of such metal or a hydrazine derivative.
While various improvements have been made on environmental, cost and photographic properties of the photothermographic material as described in the above, there still remains a room for improvement in the speed of the heat development. Using the film in the field of photoengraving such as for newspaper generally requires rapid processing of the film in pursuit of productivity. The photothermographic material, however, suffers from a problem that the dependence of line width of characters (practical sensitivity) on the energy of light exposure is larger than that of the conventional film based on chemical processing, which prevents rapid heat development at a higher line speed.
So that there is a strong need for a high-speed photothermographic material low in the exposure energy dependence and stable in the character line width, and is most suitable for photoengraving.
Another problem arises from a situation that it is not so usual that the photothermographic material is used immediately after the production, and the material is usually put into practical use after a certain duration of time while being kept wrapped and marketed. Some of the conventional photothermographic material, however, become impractical when used after a long period of storage. Thus there is a strong need for degradation resistance of the photothermographic material even in the use after a long period of storage.
It is therefore an object of the present invention to provide a photothermographic material (particularly for use in photoengraving and more particularly for use with a scanner or image setter) allowing rapid development processing while successfully suppressing widening of character line width or fogging, and having an excellent storability. It is another object of the present invention to provide a method for rapidly producing a quality image while suppressing the widening of character line width or fogging during the development process.
The present inventors found out, after extensive studies, that the foregoing object is attainable by using a photothermographic material containing a specific compound and by heat-developing such material at a high line speed of a certain range, which led us to propose the present invention.
That is, the present invention provides a method for producing an image comprising a step for heat-developing after light exposure a photothermographic material containing elsewhere on a support a non-photosensitive organic acid silver salt, a photosensitive silver halide, a nucleation aid, a binder and at least one compound expressed by the formula (A) below, at a line speed of 140 cm/min or faster: 
[where
R1, R2, R3, X1 and X2 independently represent a hydrogen atom, halogen atom, or a substituent bound via any one of carbon atom, oxygen atom, nitrogen atom, sulfur atom and phosphorus atom toa benzene ring;
at least either one of X1 and X2 is a group expressed as xe2x80x94NR4R5, where R4 and R5 independently represents a hydrogen atom, alkyl group, alkenyl group, alkynyl group, aryl group or a group expressed by xe2x80x94C(xe2x95x90O)xe2x80x94R6, xe2x80x94C(xe2x95x90O)xe2x80x94C(xe2x95x90O)xe2x80x94R6, xe2x80x94SO2xe2x80x94R6, xe2x80x94SOxe2x80x94R6 or xe2x80x94P(xe2x95x90O)(xe2x80x94R6)xe2x80x94R7, and where R6 and R7 independently represent a hydrogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, amino group, hydroxyl group, alkoxy group and aryloxy group; adjacent ones of these substituents may bind with each other to form a ring].
In the method for producing an image of the present invention, it is preferable that the photothermographic material further contains two or more compounds as expressed by the formula (1) below:
Qxe2x80x94(Y)nxe2x80x94C(Z1)(Z2)Xxe2x80x83xe2x80x83(1)
[where Q represents an alkyl group, aryl group or heterocyclic group, all of which may further have a substituent; Y represents a bivalent linking group; n represents 0 or 1; Z1 and Z2 independently represent a halogen atom; and X represents a hydrogen atom or electron attractive group].
In the method for producing an image of the present invention, the photothermographic material is preferably heat-developed at the a line speed of 140 cm/min to 700 cm/min, the light exposure is preferably effected for 10xe2x88x9215 seconds to 10xe2x88x927 seconds and at an exposure energy of 5 xcexcJ/cm2 to 1 mJ/cm2, and the light exposure is preferably effected using a multi-beam exposing apparatus provided with two or more laser heads.
The present invention also provides a high-speed photothermographic material containing elsewhere on a support a non-photosensitive organic acid silver salt, a photosensitive silver halide, a nucleation aid, a binder and at least one compound expressed by the formula (A) and two or more compounds as expressed by the formula (1). In the high-speed photothermographic material of the present invention, it is preferable that at least one compound expressed by Q is an electron attractive group expressed by the formula (1), and at least one compound expressed by Q is an electron attractive group expressed by the formula (2) below; 
[where L represents a linking group; W1 and W2 independently represent a hydrogen atom, alkyl group, aryl group or heterocyclic group; and n represents 0 or 1], and the photosensitive silver halide and binder are contained in a image producing layer of the photothermographic material, and 50 wt % or more of the binder is preferably composed of a polymer latex having a glass transition point of xe2x88x9230xc2x0 C. to 40xc2x0 C.